【简答题】一位质量m=60kg的滑雪运动员从高h=10m的斜坡自由下滑.如果运动员在下滑过程中受到的阻力F=50N,斜坡的倾角θ=30°,运动员滑至坡底的过程中,重力所做的功是( ),摩擦力所做的功是( )。
【单选题】Tom, ______ the other boys in our class, ______ playing games.
【单选题】_____ each other, the twin sisters are difficult to distinguish. [ ]
【单选题】________like singing and dancing; _________ like playing chess. [ ]
【单选题】Some people like watching TV, but _____ say it is boring. [ ]